LOCATION.-- Lat 37°54'13", long 89°50'08" (NAD of 1983), in SW 1/4 sec.24, T.7 S., R.7 W., third principal meridian, Randolph County, Hydrologic Unit 07140105, on downstream side of left pier of main truss of highway bridge at Chester, 8.1 mi downstream from Kaskaskia River, and at mile 109.9 above Ohio River.

DRAINAGE AREA.-- 708,600 mi², approximately.

PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE

DISCHARGE: October 1927 to current year. Monthly discharge only for some periods, published in WSP 1311. Since August 1873, results of discharge measurements in reports of the Mississippi River Commission.

STAGE: July 1942 to current year. Since May 1891, in reports of the Mississippi River Commission and National Weather Service.

SURFACE-WATER QUALITY

SEDIMENT: August 1980 to current year.

REVISED RECORDS.-- WDR MO-76-1: Drainage area. WDR MO-98-1: Extremes outside period of record.

GAGE.-- Water-stage recorder and U.S. Army Corps of Engineers satellite telemeter. Datum of gage is 341.05 ft above NGVD of 1929 (341.12 ft NAVD 1988). Prior to Feb. 1, 1962, nonrecording gage 0.4 mi downstream at present datum.

REMARKS.-- Natural flow of stream affected by many reservoirs and navigation dams in upper Mississippi River Basin and by many reservoirs and diversions for irrigation in Missouri River Basin.

EXTREMES FOR PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Maximum discharge, 1,000,000 ft³/s, August 7, 1993, gage height, 49.74 ft; minimum discharge, 30,000 ft³/s, December 12, 1937.

SUSPENDED-SEDIMENT CONCENTRATIONS: Maximum daily mean, 3,380 mg/L, Apr. 13, 1987; minimum daily mean, 13 mg/L, Mar. 18, 1981.

SUSPENDED-SEDIMENT LOADS: Maximum daily, 3,330,000 tons, Feb. 25, 1997; minimum daily, 3,580 tons, Mar. 18, 1981.

EXTREMES OUTSIDE PERIOD OF RECORD.--

SURFACE-WATER DISCHARGE AND STAGE: Flood of June 30, 1844, reached a gage height of 39.8 ft, discharge, 1,050,000 ft³/s, computed by the U.S. Army Corps of Engineers.